1. Field of the Invention
The present invention relates to a malfunction diagnostic apparatus for a vehicle control system.
2. Description of the Related Art
Many proposals have been made to provide such a malfunction detecting apparatus for electronically controlled engines that stores information as to the occurrence of any extraordinary (malfunction) condition of an input signal to be inputted from a sensor into an electronic control apparatus in a memory cell which can retain stored information even during interruption of power supply to the electronic control apparatus, and reads the information from the memory cell at the time of repair, thereby facilitating repair and maintenance of the electronically controlled engines.
However, there takes place such a problem that, despite the absence of malfunction with the sensor and wiring, error information is mistakenly stored due to power voltage drop (at the time of engine cranking) and an external noise; in this case, repair will be performed on the basis of this error information. To solve this conventional problem, methods for automatically or selectively erasing the stored error information have been disclosed in for example Japanese KOKAI (Disclosure) Patent Applications No. 56-34540, 58-27858, and 59-213548. These methods, however, are not able to judge if the information has been stored by mistake or is a trouble which is of low repeatability but should have been found; accordingly all of the stored important as well as wrong, unnecessary information will be cleared.
The present invention has been accomplished in an attempt to solve the above-mentioned problem, and has as its object the provision of a malfunction diagnostic apparatus for vehicle control system that is able to prevent the reading of wrong, extraordinary information.
It is another object of the present invention to provide a malfunction diagnostic apparatus that is able to acquire both the contents of the malfunction judgement and the various information comparatively corresponding to a period of vehicle operation after the judgement of malfunction. As a result, there can be realized a diagnostic apparatus that diagnoses malfunctions on the basis of information of both the contents of output code of malfunction detecting means and user's explanation of malfunction, thus preventing erroneous judgement of malfunction.